2015 GMC Sierra 2500HD Fluid Type Specs

Quick Reference

Engine Oil

For the 2015 GMC Sierra 2500HD, engine oil specifications vary significantly depending on whether you have the gasoline or diesel engine.

6.0L Vortec V8 (Gasoline): This engine requires an SAE 5W-30 viscosity grade motor oil meeting the dexos1 Gen2 specification. While dexos1 Gen3 is now the current specification, oils meeting dexos1 Gen2 are still generally acceptable and widely available. Always look for the official dexos logo on the oil container. The capacity with a filter change is approximately 6.0 quarts (5.7 liters). The oil change interval is typically indicated by the vehicle's Oil Life Monitoring (OLM) system, but generally ranges from 7,500 to 10,000 miles or once a year, whichever comes first.

6.6L Duramax V8 (Diesel): The Duramax diesel engine has more stringent requirements. It typically specifies an SAE 5W-40 or 15W-40 viscosity grade oil. The critical specification to look for is API CJ-4 or later API CK-4. Always consult your owner's manual or an authorized GMC service information portal for the most up-to-date API classification recommendation, as specifications can evolve. Using an oil that does not meet the manufacturer's specified API classification can lead to premature wear and potential warranty issues, especially with modern emissions systems. The capacity for the Duramax is a substantial 10.0 quarts (9.5 liters) with a filter change. Oil change intervals are also governed by the OLM system, but with typical heavy-duty use, intervals can range from 7,500 to 10,000 miles or 250-500 engine hours.

Common Pitfall: Never use gasoline engine oil (dexos1) in a diesel engine, or vice-versa, as their additive packages are vastly different and designed for very different combustion environments.

Engine Coolant

The 2015 GMC Sierra 2500HD uses a specific type of Organic Acid Technology (OAT) coolant known as Dex-Cool. It is typically orange or red in color. The manufacturer specification for this coolant is GM6277M. It is crucial to use only Dex-Cool or an equivalent OAT coolant that explicitly states compatibility with GM6277M. Mixing different types of coolants, especially OAT with Hybrid Organic Acid Technology (HOAT) or Inorganic Acid Technology (IAT) coolants, can lead to chemical reactions that cause gel formation, radiator clogging, and severe engine damage. The total cooling system capacity is approximately 16.8 to 19.1 quarts (15.9 to 18.1 liters), depending on the specific configuration (e.g., with or without auxiliary cooler). The recommended service interval for Dex-Cool is generally around 5 years or 150,000 miles, but always verify in your owner's manual.

Transmission Fluid

For both the gasoline and diesel engine models, the 2015 GMC Sierra 2500HD utilizes an automatic transmission that requires Dexron-VI Automatic Transmission Fluid (ATF). Dexron-VI is a fully synthetic fluid designed to provide improved friction durability, wear protection, and resistance to oxidation compared to older Dexron specifications. Never use older Dexron fluids (e.g., Dexron-III) or